A variety of elongated composite structures may have relatively confined internal cavities that require inspection in order to assure that the structure meets production and/or performance specifications. In some cases, these internal cavities are formed using flexible bladder tools which may cause dimensional variations greater than those that would result from using hard tooling. These larger dimensional variations make reliable inspection more difficult. For example, an ultrasonic probe may be moved along an internal wall of a structure to inspect an internal corner radius located a fixed distance from the probe. However, variations in wall thickness or angularity along length of the cavity may change the distance between the probe and the corner radius, which in turn may result in measurement error. While some features of the structure may be inspected by moving an external probe along outside walls of the structure, certain inconsistencies such as ply separations and voids slightly below the inside surface of the cavity may not be detected as desired.
Accordingly, there is a need for a method and device for inspecting composite structures having internal cavities that allow inspection from inside the cavity. There is also a need for a method and device for inspecting such structures from inside the cavity that allows a substantially constant distance to be maintained between inspection probe and the features of interest being inspected, in spite of variations in the cross sectional size or shape of the structure along its length.